GONIOPOEA. 27 



believing that the genus is far richer in variations than those which we have been able to 

 record here. We have, however, discovered enough to settle the old controversy mentioned in 

 the historical review, see pp. 11 and 12, as to whether the uppermost or the lateral calicles are 

 the older or the younger. The problem was rendered of special interest owing to the remark- 

 able and unaccountable structural differences between them. The belief that this difference was 

 a mere question of age was a perfectly natural one. This we have now been able to show not 

 to be the case. If, however, we now put the question, where are the youngest calicles to be 

 found ? the simple answer is, where the last budding took place. This would be in most cases 

 at the tops of the stocks where growth is most rapid, but it might at any moment be at the 

 sides if a new edge was being formed. But the budding on the top does not produce the same 

 kind of calicle as the synchronous budding at the sides, for the former produce the specialised 

 calicles characteristic of the specimen, and the budding of the edges produces calicles of the 

 low, thick-walled primitive type. These latter, however, are modified so as in most cases to 

 show their genetic affinity with those of the central region.* 



IV. ON THE POSITION OF THE FAMILY AND GENUS IN THE 

 MADREPORARIAN SYSTEM. 



The eight years' study which the present writer has given to the family Poritidae and 

 the allied Madreporida has convinced him that both these families are to be deduced from 

 some form or forms in which the septa rose from a flattened epitheca, as originally explained 

 in 1898.t But working at that time chiefly with the genus Porites, he was disposed to regard 

 it as the primitive Poritid genus and as consisting of colonies of Madreporids, the skeletons of 

 which remained in a rudimentary condition, owing to very early budding. This, it was 

 suggested, would account on the one hand for the poor development of the septa and the 

 extraordinary shallowness of the calicle, and on the other for the fact that the polyps rise high 

 above the skeleton and are unable to completely retract below the level of the walls. The 

 genus Gonio'pora might be deduced, it was thought, by secondary increase in size ; although 

 the possible truth of the suggestion made by Dana (' Zoophytes,' p. 407) was admitted— 

 that Goniopora might have had a separate origin, viz. from some Caryophyllid Dana 

 (= Eupsammiid M.-E. & H.), among which it would hold a place similar to that occupied by 

 Porifes among the Madreporacese. If this were so, the family would be an artificial one. 

 My present view is that the genus Goniopora is the more primitive, and may be regarded as 

 made up of astrajiform colonies of some simple Eupsammiid, and that Porites is derived from 

 it (see Sec. III. p. 21). 



The study of the fossil forms of Goniopora lends strong support to this view. Many of 

 the early forms, viz. the two from Sind called by Duncan '' Litharcea cpithxata" and 



* For further morphological details see Analytical Tables III. and IV. 



t .Jour. Linn. Soc, xxvii. p. 128. 



E 2 



